[ios] Fix "return foo = nil" introduced by ARC conversion tools.

ios/chrome/browser/passwords/password_generation_prompt_view.mm

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/chrome/browser/passwords/password_generation_prompt_view.h"
 
 #include <memory>
 
 #include "base/strings/sys_string_conversions.h"
 #include "components/strings/grit/components_strings.h"
@@ skipping 182 matching lines @@
 
   NSMutableAttributedString* string = [[NSMutableAttributedString alloc]
       initWithString:l10n_util::GetNSString(
                          IDS_IOS_GENERATED_PASSWORD_PROMPT_TITLE)
           attributes:attrsDictionary];
 
   UILabel* titleLabel = [[UILabel alloc] init];
   [titleLabel setAttributedText:string];
   [titleLabel setNumberOfLines:0];
   [titleLabel sizeToFit];
-  return titleLabel = nil;
+  return titleLabel;
 }
 
 - (UILabel*)passwordLabel:(NSString*)password {
   UILabel* passwordLabel = [[UILabel alloc] init];
   [passwordLabel setText:password];
   [passwordLabel setTextColor:UIColorFromRGB(kPasswordLabelFontColor)];
   [passwordLabel setFont:[[MDCTypography fontLoader]
                              regularFontOfSize:kPasswordLabelFontSize]];
   [passwordLabel setNumberOfLines:1];
   [passwordLabel sizeToFit];
-  return passwordLabel = nil;
+  return passwordLabel;
 }
 
 - (UITextView*)description {
   NSRange linkRange;
   NSString* description = ParseStringWithLink(
       l10n_util::GetNSString(IDS_IOS_GENERATED_PASSWORD_PROMPT_DESCRIPTION),
       &linkRange);
 
   NSMutableParagraphStyle* paragraphStyle =
       [[NSMutableParagraphStyle alloc] init];
@@ skipping 161 matching lines @@
                                                metrics:metrics
                                                  views:views]];
   [self addConstraints:[NSLayoutConstraint
                            constraintsWithVisualFormat:@"H:|[view]|"
                                                options:0
                                                metrics:nil
                                                  views:views]];
 }
 
 @end